1. Field of the Invention
The present invention relates to a fuel pump adapted to suck in and discharge a fuel such as gasoline. More specifically, the present invention relates to a structure for liquid-tightly securing a terminal plate to a body upper for closing one end of the fuel pump body.
2. Discussion of Related Art
There is known a fuel pump in which a fuel pump part and a driving motor part are mounted into an approximately cylindrical housing to form a fuel pump body, and a body upper is secured to an open end of the cylindrical fuel pump body that is remote from the fuel pump part to close the open end. This type of fuel pump uses a terminal plate to connect the motor part to an external power supply. The terminal plate is disposed to extend through the body upper. The brush of the motor part is connected to a portion of the terminal plate that is inside the body upper. A connector for connecting to the external power supply is connected to a portion of the terminal plate that is outside the body upper.
The terminal plate needs to be liquid-tightly secured to the body of the body upper (hereinafter referred to as xe2x80x9cbody upper blockxe2x80x9d). Therefore, it is general practice to insert-mold a metallic terminal plate into the body upper block when injection-molded from a resin material. Japanese Patent Application Unexamined Publication (KOKAI) No. Hei 11-44270 discloses a technique wherein a terminal plate is secured by the following method instead of employing the insert molding process. That is, a terminal plate insertion hole is previously provided in a body upper block when molded from a resin material. Thereafter, a terminal plate is press-fit into the insertion hole, which has been formed in the body upper block.
The conventional practice of insert-molding a metallic terminal plate into a body upper block when molded from a resin material enables the terminal plate and the body upper block to contact each other in a liquid-tight state. However, the production cost increases unfavorably.
The technique wherein a terminal plate is press-fit into an insertion hole previously formed in a body upper block when molded from a resin material has a possibility of the terminal plate becoming dislodged from the body upper block. To avoid this problem, an extra component such as a coil is needed. Accordingly, the costs also increase unfavorably.
The present inventors conceived of a structure in which a sidewardly projecting portion having springy properties is formed on the terminal plate, thereby enabling the terminal plate to be mounted and prevented from being dislodged simply by press-fitting the terminal plate into the body upper block. However, our experiments revealed that the projecting portion for preventing dislodging damages the body upper block when the terminal plate is press-fit thereinto, so that the terminal plate cannot be placed in liquid-tight contact with the body upper block. It is difficult to prevent the terminal plate from being dislodged while ensuring the required liquid-tightness.
The present invention has overcome the above-described difficulty and realized a structure in which the terminal plate is mounted to the body upper block so as to be prevented from being dislodged simply by press-fitting the terminal plate into the body upper block, and the terminal plate is placed in liquid-tight contact with the body upper block.
In the present invention, a cut and raised portion is formed on the terminal plate. The term xe2x80x9ccut and raised portionxe2x80x9d as used herein means a structure formed by making a U-shaped cut in a plate-shaped member and bending a portion of the plate-shaped member surrounded by the U-shaped cut to turn about the side left uncut. The bent portion has springy properties. The cut and raised portion is used to prevent the plate-shaped member as inserted into a slit from being dislodged. When the plate-shaped member is inserted into the slit in such a manner that the end of the bent portion closer to the connected side is the leading end, the sidewardly projecting portion is pressed closed by the wall of the slit and allowed to pass through the slit in the closed state. After passing through the slit, the closed portion is allowed to project sidewardly by the springy properties. Once it has projected, the sidewardly projecting portion disables the plate-shaped member from coming out of the slit.
The cut and raised portion offers an excellent dislodging preventing effect despite its simple structure. However, when this structure is applied to the engagement between the terminal plate and the body upper block to which the present invention is directed, the cut and raised portion provided on the terminal plate may damage the body upper block when the terminal plate passes through a through-hole for insertion of the terminal plate, which is provided in the body upper block. Therefore, the conventional structure employing the cut and raised portion cannot be used as it is.
The fuel pump according to the present invention solves the above-described technical problems. The fuel pump has an approximately cylindrical fuel pump body in which a fuel pump part and a driving motor part are mounted. The fuel pump further has a body upper for closing one end of the fuel pump body. The body upper has a body upper block made of a resin material and a terminal plate extending through the body upper block. The terminal plate has, in order from the side thereof remote from the fuel pump body, a connector fitting portion projecting from the body upper block to the outside of the fuel pump; a cut and raised portion opening toward the fuel pump body; and a thick-walled portion greater in thickness than the connector fitting portion. The body upper block has an outer shape for closing the one end of the approximately cylindrical fuel pump body. The body upper block further has a terminal plate through-hole. The terminal plate through-hole has, in order from the side thereof remote from the fuel pump body, a step portion for abutting against the cut and raised portion opening toward the fuel pump body; a projection for contacting the cut and raised portion to close it; and a press-fit portion for liquid-tightly contacting the thick-walled portion of the terminal plate.
In the fuel pump according to the present invention, the thick-walled portion of the terminal plate is pressfit into the press-fit portion of the body upper block to bring the thick-walled portion and the press-fit portion into liquid-tight contact with each other, thereby ensuring the required liquid-tightness between the terminal plate and the body upper block. In addition, the terminal plate is formed with a cut and raised portion for preventing dislodging, and the terminal plate through-hole provided in the body upper block is formed with a step portion engageable with the cut and raised portion of the terminal plate to disable the terminal plate from coming out of the body upper block. When the terminal plate is inserted into the terminal plate through-hole from the fuel pump body side of the body upper block, the cut and raised portion is closed by being pressed with the inner wall of the terminal plate through-hole. When the terminal plate is further inserted, the cut and raised portion reaches beyond the forward end of the step portion and opens to engage with the step portion. Once this state has been established, the terminal plate is disabled from being pushed back toward the fuel pump body.
If the cut and raised portion of the terminal plate contacts the press-fit portion of the body upper block when it passes through the terminal plate through-hole of the body upper block, the press-fit portion may be damaged. In such a case, the terminal plate cannot be placed in liquid-tight contact with the body upper block. In the present invention, however, the cut and raised portion of the terminal plate passes through the terminal plate through-hole without contacting the press-fit portion in a state where the cut and raised portion is kept closed by contacting the projection. Therefore, there is no possibility of the cut and raised portion damaging the wall surface of the press-fit portion. Accordingly, the thick-walled portion of the terminal plate and the press-fit portion of the body upper block can be placed in liquid-tight contact with each other, and the terminal plate can be prevented from being dislodged without using other component parts.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.